The present invention relates to a method of smelting iron ore by reducing the iron ore in the presence of fixed carbon to produce elemental iron as a molten pool. More particularly the present invention relates to such a method in which the iron ore is reduced in a reactor and the fixed carbon is introduced into the reactor as hot char produced from coal that contains volatile substances. Even more particularly, the present invention relates to such a method in which volatile substances are partially oxidized to produce a fuel gas which is fed to a burner that is in turn fired into the molten pool.
Iron ore is reduced to molten iron in a bath by a variety of known processes. In all of such processes, the iron ore is reduced by supplying the iron ore and a carbonaceous reductant to a reactor in which the iron ore is reduced while being heated to form a molten pool of elemental iron and iron oxide slag. The carbonaceous reductant can be in the form of coal. Upon introduction into the molten bath, the coal would be converted in to a hot char. The principle component of the hot char are fixed carbon and ash. During the formation of this hot char, volatile substances formed from the volatile matter within the coal feed are vaporized. The vaporization of these volatile substances is endothermic and hence, not thermally efficient. In addition, it very difficult to efficiently mix this gaseous volatile matter with a gaseous oxidant and efficiently transfer the heat of combustion to the melt.
The foregoing processes require high quality coal, to wit: coal having a low volatile content. Such coal is not used in a thermally inefficient manner in that heat energy is lost in vaporizing the volatile substances. Moreover, the combustion of the volatile substances above the melt to heat the molten iron is also thermally inefficient because the heat energy is not directed into the molten iron. Therefore conventional bath smelting processes use the more costly low volatile matter coal to minimize the concentration of this troublesome component. This invention, on the other hand, allows bath smelting process to heat the molten bath using the coal volatile matter components more efficiently than with more expensive fixed carbon. Therefore, this invention makes the less expensive volatile matter components a more useful component to heat the melt than the more expensive fixed carbon components up to the bath heating requirement. However, for both this invention and the prior art, the fixed carbon components remain vital for reduction of the molten iron oxide to elemental iron.
As will be discussed, the present invention allows iron ore to be reduced in a more cost efficient manner than prior art methods because it allows a lower quality coal to be used to form the char and also permits the combustion of the volatile substances to be directed into the molten iron in a thermally efficient manner.